This application relates to a multi-speed vehicle transmission wherein the electronic control unit drives actuators for achieving operator selected shifts. The electronic control is either re-programmed or replaced to modify the number of available speed ratios within the transmission.
Multi-speed transmissions for use in heavy vehicles are becoming more and more complex. Some drivers desire fine gradations in the speed ranges available to them. Thus, there are truck transmissions in service that provide 18 different speeds to a driver. At the same time, other drivers may not wish to have such a wide range of speed ratios. The number of different speed ratios does not effect the available speed provided to the output of the vehicle. Instead, additional speed ratios provides additional fractional increments of the maximum vehicle speed ratio.
The typical 18-speed truck transmission includes a main transmission gear box which would have five different selectively engagable gears to provide five different basic speed ratios. A range section then modifies those five different speeds between a high and a low range to double the number of available speeds. Thus, in transmissions having five main gears and a high/low range box, there are actually ten available speed ratios.
Another transmission option is the use of a splitter gear. The splitter gear provides effectively the opposite of the range box. That is, the splitter gear splits the speed ratios between each of the five main gears in the main transmission. In this way, the splitter also doubles the number of available speed ratios.
In some driving applications, it may be desirable to have more speed ratios. As an example, when driving through mountains some drivers may wish to have more available speed ratios. On the other hand, the increased number of speed ratios may be undesirable during flat landscape driving situations. Moreover, some drivers simply do not wish to have 18 available speeds as it may complicate shifting between the speeds.
Thus, at present, truck drivers may purchase a truck having only a ten-speed transmission if the particular truck owner only desires ten available speeds. At resale time, this may limit the resale value of the truck as it would be attractive to a truck owner desiring 18 available speeds.
Moreover, it is difficult for a vehicle manufacturer to tailor the number of available speeds to the individual customer. Changing the number of available speeds effectively requires changing the type of transmission incorporated into the vehicle. That is, a truck manufacturer may have one customer that only wants ten available speeds and a second customer that would like 18 available speeds. Until now, the only way of achieving this option would be to provide different transmissions in those vehicles.